Dispersion of synthetic polymeric materials



Patented Mar. 5,1940 I IUNITED'STATES PATENT OFFICE DISPERSION OF SYNTHETIC POLYMERIC MATERIALS James Emory Kirby, Wilmington, Del., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application August 14, 1936, Serial No. 96,051

7 Claims. (Cl. 260-8) This invention relates to the preparation of medium in which dispersions the particles of aqueous dispersions of halogen-Z-butadieneschlorobutadiene bear a positive charge. A furl,3 and their polymers. More particularly, it rether object is to polymerize halogen-2-.-butalates to the preparation of aqueous dispersions dienes-1,3 whilethey are dispersed in aqueous of halogen-2-butadienes-1,3 and their polymers media in which the particles of the dispersed halin which dispersions the particles of the monomer ogenbutadiene bear a positive charge. A still furor polymer bear a positive charge. Still more ther object is to prepare dispersions of halogen-2- particularly the invention relates to the polybutadiene-1,3 polymers in an aqueous medium in merization of halogen-2-butadienes-L3 while which dispersions the particles of polymer bear a 10 they are dispersed in an aqueous acid medium positive charge. Another object is to prepare 10 in which their particles bear a positive charge. aqueous acid dispersions of halogen-Z-butadiene- This application is a continuation-in-part of a 1,3 polymers and particularly of chloro-2-butacopending application, Serial No. 572,739, filed diene-l,3 polymers in which dispersions the poly- November 2, 1931, now matured into U. S. Patent mer particles are positively charged and which No. 2,076,949, granted April 13, 1937. dispersions are stable to added acid. Other ob- 15 It has been discovered, as disclosed by Carothjects will appear hereinafter. ers and Collins in U. S. Patent No. 1,950,431, that It has now been found that these objects may hydrogen halides such as hydrogen chloride and be accomplished by dispersing a halogen-2-butahydrogen bromide may be made to combine with dime-1,3, for example, chloro-2-butadiene-l,3, in

monovinylacetylene under suitable conditions a suitable aqueous medium, for example, an aquewith the formation of chloro-2-butadiene-1,3 ous acid solution of casein, and thereafter polya-nd bromo-2-butadiene-L3, respectively. Caromerizing the dispersed halogen-2-butadiene-1,3. thers and Collins have further disclosed in U. S. It is also possible to prepare aqueous acid disper- Patent No. 1,950,432 that chloro-2-butadiene-1,3 sions of hal0gen-2-butadiene-1,3 polymers, in

may be polymerized under avariety of conditions. which the particles of polymer are positively A similar disclosure as regards bromo-2-butacharged by adding dilute acid to an alkaline disdiene-1,3 is found in U. S. Patent No. 1,950,433 of persion of a halogen-2-butadiene-l,3 polymer unthe same inventors. der conditions which render the dispersion rela- It has also been disclosed by Collins in his U. S. tively insensitive to coagulation by acid. Such Patent No. 1,967,861 that chloro-2-butadiene-1,3 conditions may be produced by adding a small so is readily dispersed in anaqueous medium and amount of gelatin to the alkaline dispersion bepolymerized in that state to yield an artificial lafore adding the acid. The dispersed polymer partex from which a rubber-like material may be obticles in acid dispersions so prepared bear a positained. In this patent, Collins more particularly tive charge even though the particles in the alkadiscloses that in certain caseseven though the disline dispersions from which they are prepared 35 persion of chloro-2-butadiene-1,3 is alkaline bebear a negative charge. fore polymerization it may become acid (show a The following examples describe in detail methpH of less than 7) during the course of the polyods for accomplishing the above objects, but it is merization due to the gradual liberation of acid. to be understood that they are inserted merely The particles of this acid dispersion have been for purposes of illustration and are not to be con- 0 found to bear a negative charge and the general strued as limiting the scope of the invention. instability of the latices in this condition greatly Example I retards their value.

In none of these references, however, is there one p Of casein is dissolved in 52 Parts Of any disclosure of a method for preparing disperglacial acetic acid and 130 parts of water. Fortysions of chloro-2-butadiene-1,3 polymer in which six (46) parts of chloro 2-butadiene-1,3 are then the particles are positively charged. Such disperdispersed in this solution with constant rapid stirsions have been found to have very useful properring. A homogeneous emulsion results. In about ties m e fully set forth hereinafter. two days at room temperature the polymerization 50 It is, therefore, an object of this invention to is complete and a pure white, finedispersion of 5 p p dispersions of ha108en-2-bl1tadieneS-L3 chloro-2-butadiene-1,3 polymer is obtained. in an aqueous medium in which dispersions the E l H particles of the halogenbutadiene bear a positive :camp 8 charge. A more specific object is to prepare dis- Five parts of gelatin dissolved in 100 parts of persions of chloro-2-butadiene-1,3 in an aqueous water are added to parts of an aqueous alkadispersion of chloro-2-butadiene-1,3 to which the gelatin and acid were added in this example was prepared with sodium oleate as the emulsifying agent.

The use of chloro-2-butadlene-1,3 in the above examples indicates the manner in which the invention may be applied. The invention is not limited to the use of chloro-2-butadiene-L3 however, but is broadly applicable to halogen-2-butadimes-1,3. Thus bromo-2-butadiene-1,3 may be treated in the same manner as the chloro-derivative to yield aqueous acid dispersions.

In addition to the media illustrated in the above examples, the following are given as further illustrations of media in which the emulsified polymer particles carry a positive charge. The invention is not limited to the use of the specific aqueous media disclosed, however. Thus, the aqueous media disclosed in Examplesl'. and II may be varied by substituting another acid for the acetic and sulfuric acids used. Hydrochloric and other hydrohalogen acids may, for example, be used. Moreover, as disclosed in a copending application of Dales and Downing, Serial No. 128,630, filed March 2, 1937, a wide variety of other dispersion media in which the halogenbutadiene polymer particles bear a positive charge are obtained by dissolving in water salts of inorganic acids and organic bases of high molecular weight.

Suitable proportions of casein or gelatin, for example, are indicated by the above examples. The invention is not limited to the particular proportions given in the examples. It is. possible to obtain satisfactory results with somewhat iess amounts as well as with greater amounts. The acidity of the dispersion media illustrated above may vary but should not be too great since this develops a tendency to instability. A preferred acidity is that obtained with the proportions of ingredients used in Example I. In its broad scope, moreover, the invention is not limited-to dispersion media of any particular hydrogen ion conceneration but includes both acid and alkaline dispersions.

The concentrations of the halogen-Z-butadienes-1,3, particularly the chloro-derivative, which may be used, will vary widely from those given in the above examples. About 20% of chloro-2-butadiene-L3 as used in Example I gives good results but greater or lesser concentrat-ions are operable.

The dispersion is preferably prepared by passing the chloro-2-butadiene-L3 into the dispersion medium slowly with rapid stirring. Other means for preparing dispersions, familiar to the art, may be used, however.

Polymerization proceeds spontaneously in the absence of inhibitors and is generally complete in about two days. This rate may be increased by the use of catalysts such as air, oxygen, heat, pressure, etc. as desired.

When polymerization is complete a. fine, pure white dispersion results in most cases. A similar dispersion is obtained by the method of Example II, which is likewise susceptible of wide variation. Furthermore, a wide variety of alkaline or neutral halogen-2-butadie'ne-L3 polymer latices can be thus converted to acid latices, for example, dispersions made with emulsifying agents, such as salts of alkyl naphthalene sulfonic acids and the like.

aieasis The aqueous dispersions of the polymer, obtained by the process of this invention may be used, as such, directly for the preparation of a wide variety of articles. If desired an antioxidant such as catechol, pyrogallol, or eugenol may be added. They may also be compounded and coagulated by variousmeans in the form of films or shaped articles as, for example, by extrusion into a coagulating bath or by the method disclosed in copending application Serial No.

' 572,739, mentioned above, which involves dipping a form into the latex and then coagulating the film so formed. In general, the art relating to the formation of useful articles from latices of.

natural rubber may be applied to the latices obtained by the process of this invention.

Thus many of these aqueous polymer dispersions may be coagulated bystrong electrolytes,

such as solutions oi sodium chloride, sodium sulfate or calcium chloride or by organic solvents miscible with water but which are not solvents for the polymer, for example, ethanol, methanol, acetone, etc. It is also possible to coagulate some of the acid dispersions with alkali. Some dispersions coagulate, of course, more readily than others depending upon their stability. Suitable means for coagulating a particular dispersion will be apparent to those skilled in the art. Rubber-like products of predetermined shape may be prepared by evaporating the dispersion on the surface of forms or with the. aid of suction on porous forms.

As disclosed above, the dispersed particles of polymer show a positive'charge in the dispersions of this invention. In this, these dispersions are novel as well as peculiarly useful. The fact that the dispersed particles do carry a positive charge can be readily demonstrated by passing a direct electric current through a small portion of the dispersion which can be viewedthrough a microscope. It will be noted that the particles migrate,

toward the negatively charged electrode.

The presence of the positive charge on the particles not only makes it possible to incorporate certain compounding ingredients, such as alumina, which are difficult to incorporate in negatively charged latices but in addition makes it possible to produlce mutual coagulation on forms by bringing these latices into contact with negatively charged latices. In addition, acid latices made by the process of the above examples may be mutually coagulated with alkaline latices. In some cases, these latices show improved wetting properties particularly on glass. Many other uses and advantages accruing from the inherent properties of these latices will be apparent to those skilled in the art.

It is apparent that many widely different embodiments of this invention may be made without departing from the spirit and scope thereof and therefore it is not intended to be limited except as indicated in the appended claims.

I claim:

1. An aqueous dispersion of a halogen-Z-butadiene-1,3 in which the dispersed particles carry a positive charge.

2. An aqueous acid dispersion of chloro-2-butadiene-1,3 in which the dispersed particles carry a positive charge.

3. An aqueous dispersion'of a polymer of a halogen-2-butadiene-l,3 in which the particles of polymer carry a positive charge.

4. An aqueous dispersion of a polymer of chloro-2-butadiene-1,3 in which the particles of polymer carry a positive charge.

5. An aqueous acid dispersion of a polymer of chloro-2-butadiene-L3 in which the particles of polymer carry a positive charge.

6. An aqueous acid dispersion of a polymer of chloro-2-butadlene-L3 containing an amount of gelatin such that the ratio of gelatin to chloro-2- butadiene-L3 is between 1:48 and 5:49 in which dispersion the particles of polymer carry a positive charge.

7. An aqueous acid dispersion of a polymer of chloro-2-butadiene-1,3 containing an amount of casein such that the ratio of casein to chloro-2- butadiene-1,3 is between 1:46 and 5:49 in which dispersion the particles of polymer carry a posi- 6 tive charge.

JAMES EMORY KIRBY. 

